Plunger rod comprising at least three annular elements for a prefilled syringe

Abstract

A prefilled syringe includes a syringe body filled with a medical fluid, which has a nozzle at a front side, the nozzle being closed with a cap, and which is closed at a rear side with a displaceable plunger; and a plunger rod that can be inserted into the syringe body via the rear side. The plunger rod has a connecting portion at a front side, via which the plunger rod can be connected to the plunger. At least three annular elements, which extend at least in some sections about a longitudinal axis of the rod, are arranged on a rear side of the connecting portion on the plunger rod in such a manner that they are located in the syringe body when the plunger rod is fully connected to the plunger. The three annular elements support a coaxial connection of the rod to the plunger positioned in the syringe.

The invention claimed is: 
     
       1. A prefilled syringe comprising
 a syringe body which is filled with a medical fluid and comprises on a front end a nozzle, which is closed by way of a cap, and is closed on a rear end by way of a displaceable plunger, 
 a plunger rod which is insertable into the syringe body via the rear end and comprises on a front end a front-end connecting portion, by means of which the plunger rod is connectable to the displaceable plunger, wherein at least three annular elements configured to guide the plunger rod in the syringe body, which extend at least in portions about a longitudinal axis of the plunger rod, are arranged on the plunger rod on a rear end of the connecting portion such that when the plunger rod is fully connected to the plunger, the at least three annular elements are situated in the syringe body; wherein the at least three annular elements extend at least in portions about a longitudinal axis of the plunger rod and are arranged at a distance R, wherein 0.5 mm≤R≤20 mm. 
 
     
     
       2. The prefilled syringe as claimed in  claim 1 , wherein a position of the plunger in the prefilled syringe body and the position of the at least three annular elements on the plunger rod are matched to one another such that in a first step, when the plunger rod is placed by way of its connecting portion on the plunger, two of the at least three annular elements are arranged in the interior of the syringe body. 
     
     
       3. The prefilled syringe as claimed in  claim 2 , wherein an outside diameter (D) of the at least three annular elements and an inside diameter of the syringe body are selected to enable the at least three annular elements to engage the syringe body. 
     
     
       4. The prefilled syringe as claimed in  claim 2 , wherein an outside diameter (D) of the at least three annular elements is identical. 
     
     
       5. The prefilled syringe as claimed in in  claim 2 , wherein wing elements, which extend radially outwardly and connect the at least three annular elements together, are arranged distributed over a circumference of the plunger rod. 
     
     
       6. The prefilled syringe as claimed in in  claim 5 , wherein the wing elements are individually arranged between the at least three annular elements. 
     
     
       7. The prefilled syringe as claimed in in  claim 2 , wherein at least four wing elements are arranged to form angles therebetween, each angle being 90°, wherein the at least four of the wing elements are arranged between two of the at least three annular elements. 
     
     
       8. The prefilled syringe as claimed in  claim 1 , wherein an outside diameter (D) of the at least three annular elements and an inside diameter of the syringe body are selected to enable the at least three annular elements to engage the syringe body to permit guiding the plunger rod in the syringe body. 
     
     
       9. The prefilled syringe as claimed in  claim 1 , wherein an outside diameter (D) of the at least three annular elements is identical. 
     
     
       10. The prefilled syringe as claimed in in  claim 1 , wherein wing elements extend radially outwardly and connect the at least three annular elements together, the wing elements being arranged distributed over a circumference of the plunger rod. 
     
     
       11. The prefilled syringe as claimed in in  claim 10 , wherein at least four of the wing elements are arranged to form angles therebetween, each angle being 90°, wherein the at least four of the wing elements are arranged between two of the at least three annular elements. 
     
     
       12. The prefilled syringe as claimed in  claim 10 , wherein an outside diameter (D F ) of the wing elements is selected to enable the wing elements to engage the syringe body. 
     
     
       13. The prefilled syringe as claimed in  claim 10 , wherein an outside diameter (D F ) of the wing elements is substantially the same as the outside diameter (D) of the at least three annular elements. 
     
     
       14. The prefilled syringe as claimed in  claim 10 , wherein an outside diameter (D F ) of the wing elements is smaller than an outside diameter (D) of the at least three annular elements. 
     
     
       15. The prefilled syringe as claimed in in  claim 10 , wherein an outside diameter (D F ) of the wing elements is less than an outside diameter (D) of the at least three annular elements by between 1 mm and 10 mm. 
     
     
       16. The prefilled syringe as claimed in in  claim 10 , wherein the wing elements are individually arranged between the at least three annular elements. 
     
     
       17. The prefilled syringe as claimed in in  claim 10 , wherein an outside diameter (D F ) of the wing elements is less than an outside diameter (D) of the at least three annular elements by between 4 mm and 8 mm. 
     
     
       18. The prefilled syringe as claimed in in  claim 1 , wherein the plunger rod is premounted on the plunger. 
     
     
       19. The prefilled syringe as claimed in  claim 1 , wherein the plunger rod is located next to the syringe body in an oxygen-impermeable, over pack. 
     
     
       20. An oxygen-impermeable over pack having an interior in which the syringe as claimed in  claim 1 , wherein it is hermetically enclosed. 
     
     
       21. A pre-filled syringe as claimed in  claim 1 , wherein the at least three annular elements are arranged on the plunger rod such that, when the plunger rod is fully connected to the plunger, the at least three annular elements are situated in the syringe body. 
     
     
       22. A plunger rod for a prefilled syringe as claimed in  claim 1 , wherein 1 mm≤R≤10 mm.